Improve performance of Defaults.updates()

Sources/Defaults/Defaults.swift

@@ -239,7 +239,7 @@ extension Defaults {
  initial: Bool = true
  ) -> AsyncStream<Value> { // TODO: Make this `some AsyncSequence<Value>` when Swift 6 is out.
  .init { continuation in
- let observation = UserDefaultsKeyObservation(object: key.suite, key: key.name) { change in
+ let observation = UserDefaultsKeyObservation2(object: key.suite, key: key.name) { change in
  // TODO: Use the `.deserialize` method directly.
  let value = KeyChange(change: change, defaultValue: key.defaultValue).newValue
  continuation.yield(value)
@@ -275,7 +275,7 @@ extension Defaults {
  ) -> AsyncStream<Void> { // TODO: Make this `some AsyncSequence<Value>` when Swift 6 is out.
  .init { continuation in
  let observations = keys.indexed().map { index, key in
- let observation = UserDefaultsKeyObservation(object: key.suite, key: key.name) { _ in
+ let observation = UserDefaultsKeyObservation2(object: key.suite, key: key.name) { _ in
  continuation.yield()
  }
 

Sources/Defaults/Observation.swift

@@ -180,7 +180,7 @@ extension Defaults {
  }
 
  guard
- selfObject == object as? NSObject,
+ selfObject == (object as? NSObject),
  let change
  else {
  return
@@ -191,6 +191,69 @@ extension Defaults {
  guard !updatingValuesFlag else {
  return
  }
+
+ callback(BaseChange(change: change))
+ }
+ }
+
+ // Same as the above, but without the lifetime utilities, which slows down invalidation and we don't need them for `.updates()`.
+ final class UserDefaultsKeyObservation2: NSObject {
+ typealias Callback = (BaseChange) -> Void
+
+ private weak var object: UserDefaults?
+ private let key: String
+ private let callback: Callback
+ private var isObserving = false
+
+ init(object: UserDefaults, key: String, callback: @escaping Callback) {
+ self.object = object
+ self.key = key
+ self.callback = callback
+ }
+
+ deinit {
+ invalidate()
+ }
+
+ func start(options: ObservationOptions) {
+ object?.addObserver(self, forKeyPath: key, options: options.toNSKeyValueObservingOptions, context: nil)
+ isObserving = true
+ }
+
+ func invalidate() {
+ if isObserving {
+ object?.removeObserver(self, forKeyPath: key, context: nil)
+ isObserving = false
+ }
+
+ object = nil
+ }
+
+ // swiftlint:disable:next block_based_kvo
+ override func observeValue(
+ forKeyPath keyPath: String?,
+ of object: Any?,
+ change: [NSKeyValueChangeKey: Any]?, // swiftlint:disable:this discouraged_optional_collection
+ context: UnsafeMutableRawPointer?
+ ) {
+ guard let selfObject = self.object else {
+ invalidate()
+ return
+ }
+
+ guard
+ selfObject == (object as? NSObject),
+ let change
+ else {
+ return
+ }
+
+ let key = preventPropagationThreadDictionaryKey
+ let updatingValuesFlag = (Thread.current.threadDictionary[key] as? Bool) ?? false
+ guard !updatingValuesFlag else {
+ return
+ }
+
  callback(BaseChange(change: change))
  }
  }

Sources/Defaults/Utilities.swift

@@ -1,10 +1,8 @@
 import Foundation
 import Combine
-#if DEBUG
-#if canImport(OSLog)
+#if DEBUG && canImport(OSLog)
 import OSLog
 #endif
-#endif
 
 
 extension String {